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Ottawa River

geography Maturity 7-9 Next article →

The Ottawa River is a major waterway in Eastern Canada. It flows through the provinces of Ontario and Quebec. For most of its length, the river acts as a border between these two provinces. It is the longest river in Quebec. The river is also a major tributary to the St. Lawrence River. Its name comes from an Algonquin word meaning "to trade." This name reflects its history as a primary trade route.

Ottawa River from satellite
Ottawa River from satellite

The river follows a path through a unique geological feature. This feature is the Ottawa-Bonnechere Graben. The map shows this rift valley, which formed 175 million years ago.

Ottawabonnecheregrabenmap
Ottawabonnecheregrabenmap

Much of the river flows through the Canadian Shield. However, lower sections flow through limestone plains and glacial deposits. During the last ice age, the valley was depressed below sea level. As the massive glaciers began to retreat, the valley filled with sea water.

Forests cover much of the land around the river. These forests formed over thousands of years. They grew as trees recolonized the Ottawa Valley after the ice age. You can find coniferous forests in many areas. These forests consist of trees like pine. They often grow on old sand plains or in wet areas with clay substrate. You can also find deciduous forests in areas with better soil. These forests are dominated by birch, maple, beech, oak, and ash trees.

ottawarivermattawa
ottawarivermattawa

Human activity has changed these natural forests over time. Early loggers exploited the vast areas of pine trees. Later generations of loggers removed hemlock trees. They used the wood for tanning leather. This created a permanent deficit of hemlock in most forests. Logging and early settlement were also linked to large wildfires. These fires removed forests and led to soil erosion. Because of this, nearly all current forests show signs of human disturbance. Most tracts of old-growth forest are now rare and important for conservation.

The river system includes many diverse wetlands. These areas are biologically very important. The Westmeath sand dune complex is known for its pristine dunes and rare plants. Shirleys Bay contains a diverse shoreline alvar and a large silver maple swamp. These wetlands rely on seasonal water fluctuations. High water levels maintain the silver maple swamps. Low water periods allow rare plants to grow on emerged sand and clay flats. There are five principal types of wetland vegetation. One is the swamp, which is mostly silver maple. The other four are herbaceous types named after dominant plants: Scirpus, Eleocharis, Sparganium, and Typha.

Water levels in the river can change significantly. The average annual mean waterflow at the Carillon dam is 1,400 m³/s. This flow can reach extremes. Since 1964, the lowest recorded level was in 2010. The highest recorded level was in 2017. The river also has varying depths. Its maximum depth is 33 meters at the Carillon Reservoir. Many different rivers flow into the Ottawa River. These are called tributaries. Major tributaries include the Gatineau, Madawaska, and Mattawa rivers.

River Ottawa (view from the Peace Tower of Parliament Centre Block)
River Ottawa (view from the Peace Tower of Parliament Centre Block)

The Ottawa River is connected to many different systems. It links the Canadian Shield to the limestone plains. It connects the inland forests to the St. Lawrence River. Even the ancient history of the Earth is visible here. You can find stromatolite beds in the river.

Ottawa River Stromatolite Bed
Ottawa River Stromatolite Bed

These are ancient structures that show the long history of life and geology in the region. The river remains a vital part of the landscape for both nature and people.

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🖼️ Images & Media (6)
File:Ottawa River from satellite.jpg
Ottawa River from satellite.jpg
File:River Ottawa (view from the Peace Tower of Parliament Centre Block).JPG
River Ottawa (view from the Peace Tower...
File:River Ottawa (view from the Peace Tower of Parliament Centre Block) 2.JPG
River Ottawa (view from the Peace Tower...
File:Ottawabonnecheregrabenmap.png
Ottawabonnecheregrabenmap.png
File:Ottawa River Stromatolite Bed.jpg
Ottawa River Stromatolite Bed.jpg
File:ottawarivermattawa.jpg
ottawarivermattawa.jpg
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